Behaviour of polygonal-shaped steel-tube columns filled with high-strength concrete

This paper presents an investigation on axially loaded polygonal-shaped steel-tube columns filled with high-strength concrete. The tubes had triangular, hexagonal and octagonal cross-sections, the concrete had a nominal concrete compressive cylinder strength of 100 MPa and the steel had a nominal yield strength of 285 MPa. For each tube cross-section, two identical specimens of concrete-filled tubes and one specimen of a hollow tube were examined. Load shortening, strain histories and failure modes were recorded and compared. Finite-element analysis with three different existing constitutive models of concrete were also developed and validated against the experimental results. The load-carrying capacities of the concrete-filled tubes were compared with the derived values from BS EN 1994-1-1: 2004, ACI 318-11/AISC 360-16 and GB 50936-2014. The feasibility of current design standards for concrete-filled steel-tube columns of different cross-sections is discussed.